Bertha starts drilling new Seattle tunnel beneath downtown

Seattle’s big dig is officially underway, as the world’s largest tunneling machine began drilling the new Highway 99 tunnel Tuesday afternoon.

The machine, dubbed “Bertha,” began its two mile journey beneath downtown starting in SoDo near Safeco Field just after 4:00 p.m.

“Her face is spinning and she’s grinding her way into the headwall,” said an excited Linea Laird, Program Administrator, shortly after Bertha got underway. “If you were closer, you could actually see her face turning and some of her teeth and bits.”

Bertha is 326 feet long and weighs 7,000 tons. It will leave a tunnel nearly 58 feet in diameter. It was built in Japan over the last two years, then shipped in pieces to Seattle where it was reassembled.

At first, she’ll move slow as crews put her through her initial paces. “Starting out, we expect a range of about six and half feet a day so it’ll be a slow start,” Laird said.

The $80 million machine is part of the $3.1 billion project to replace the Alaskan Way Viaduct, the double deck highway along the downtown Seattle waterfront. Built in 1953, it has carried 110,000 vehicles a day. Officials said the structure had to be replaced because it could collapse in an earthquake. Its removal is part of a project to renovate the waterfront, rebuilding the seawall, improving surface streets, and adding new vistas along Elliott Bay.

It’ll take about 14 months to complete the two mile tunnel as Bertha moves to the north. She’s expected to punch through to the surface near south Lake Union by October 2014. Traffic is expected to start using the four-lane toll tunnel by late 2015.

“We have another year and a half of demanding and difficult work ahead, but we’re on schedule and budget. So this is a great place to be at this moment in time, and I’m very proud of the teams and the people involved,” Laird said.